Two Tryptophans Are Better Than One in Accelerating Electron Flow through a Protein.

ABSTRACT: We have constructed and structurally characterized a Pseudomonas aeruginosa azurin mutant Re126WWCu^I , where two adjacent tryptophan residues (W124 and W122, indole separation 3.6-4.1 Å) are inserted between the Cu^I center and a Re photosensitizer coordinated to the imidazole of H126 (Re^I(H126)(CO)₃(4,7-dimethyl-1,10-phenanthroline)⁺). Cu^I oxidation by the photoexcited Re label (*Re) 22.9 Å away proceeds with a ∼70 ns time constant, similar to that of a single-tryptophan mutant (∼40 ns) with a 19.4 Å Re-Cu distance. Time-resolved spectroscopy (luminescence, visible and IR absorption) revealed two rapid reversible electron transfer steps, W124 → *Re (400-475 ps, K ₁ ≅ 3.5-4) and W122 → W124

SUBMITTER: Takematsu K 

PROVIDER: S-EPMC6346393 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature